title: The challenge of studying the effects of managed care as managed care evolves.
mesh_terms: D006302:Health Services Research / Q000592:standards; D006801:Humans; D008329:Managed Care Programs / Q000592:standards*; D018854:Managed Competition; D008389:Marketing of Health Services / Q000592:standards; D006278:Medicare / Q000592:standards*; D017146:Models, Organizational; D011635:Public Health Administration; D011787:Quality of Health Care; D014481:United States